(1) can we damage the camera/lens(es) by switching lenses without turning off the camera?

The K-7 instruction manual includes a 'caution' message: "Turn the camera off before attaching or removing the lens to prevent unexpected len movement". This is a cautious warning implying some 'lens movement' but does not mention any risk to the contacts (?). I woud have thought that the contacts would be sensitive....

(2) When the camera is in 'sleep' mode (Auto power off), would we damage the camera/lens(es) by switching lenses when the camera is asleep without turning off the camera?

The K-7 operating manual states that the Auto Power Off does "turn off" the camera if unsused after a certain length of time. Is this truly equivalent to a hard switch/power off?

While I am trying to take care of my gears, I found myself a couple of times switching lenses while the camera was 'asleep', in the rush of the action.

I would be keen to hear from experienced Pentax users. Thank you in advance for your input.

I would not take the chance, personally. Since I keep holding the camera in my right hand when I change lenses (I push the release button with my little finger), it's become 2nd nature to turn the switch to off with my index before I grab the lens to remove it.

I think the big concern is that the sensor builds a static charge when turned on, so it attracts dust particles when the lens is off. I've personally seen this. My buddy was fooling with the camera and took the lens off while it was turned on. Immediately I got a big dust goober stuck on the sensor. So don't do it.

My experience was years ago with a K110D. I think that some of the more recent cameras—especially the top tier models—will have SMC applied to the sensor. SMC helps repel dust, I think. If I remember right, the K110D didn't have a multi-coated sensor, but the K10D did. I never had a problem with dust on the K10D, or the K20D, or the K-7, or the K-x. Maybe they are more dust repellant.

Yes I am sure many if us have done this accidentally a few times. I have not noticed any ill effects to my camera or average AF lenses.
But of course habitually my grip is one finger turns off the camera then one finger releases the lens lock.

I think the big concern is that the sensor builds a static charge when turned on, so it attracts dust particles when the lens is off. I've personally seen this. My buddy was fooling with the camera and took the lens off while it was turned on. Immediately I got a big dust goober stuck on the sensor.

Aegon wrote: I think the big concern is that the sensor builds a static charge when turned on, so it attracts dust particles when the lens is off.

I was reading on another forum that this is a commonly attributed fallacy, and that in reality there is NO STATIC CHARGE applied to the sensor's antialiasing screen at power on status. Perhaps those more technically inclined will comment on this????

Well have you ever tried to clean a sensor? A blower alone won't clean it very well. Given that the sensor is not adhesive and that dust is not adhesive, there must be something to explain why a strong blow from a rocket blower isn't enough to remove a goober. It seems like some other force is involved.

Please post a link to the scientific article that says static charge on the sensor is a fallacy. I'd like to see it to see who wrote this article so I can decide if he is trustworthy, and if his methods are trustworthy.

In my experience, changing lenses while leaving the power on leads to dust on the sensor. On the other hand, changing lenses with the power off has not yet lead to dust on the sensor for me. So my real world experience suggests that the best thing to do is to turn the camera off.

Ya'll can do whatever you want. But I find it easy enough to turn the camera off.

I think the reason for this warning is that if you have the camera in autofocus mode, and the camera is not in "sleep" then there is a faint possibility of the lens trying to focus at the exact same time as you are removing the lens. I imagine that it could possibly place some stress on the autofocus mechanism of the lens. While I sincerely doubt the likelyhood of such a series of events, the possibility may be there, and hence the warning in the manual.

Static Charge by definition (simple) is an electrical charge at rest. In other words, not moving. It stays that way until a foreign force acts or interacts with it. Drag your feet across the carpet and touch a brass doorknob. The theory is that the sensor has a charge and so does the dust. First of all, dust has to be in the mirror box at the time the shutter opens for it to get On the sensor (screen). It is entirely reasonable though for the electrical charge of the sensor to attract a particle of dust when the shutter opens.

Well have you ever tried to clean a sensor? A blower alone won't clean it very well. Given that the sensor is not adhesive and that dust is not adhesive, there must be something to explain why a strong blow from a rocket blower isn't enough to remove a goober. It seems like some other force is involved.

Please post a link to the scientific article that says static charge on the sensor is a fallacy. I'd like to see it to see who wrote this article so I can decide if he is trustworthy, and if his methods are trustworthy.

In my experience, changing lenses while leaving the power on leads to dust on the sensor. On the other hand, changing lenses with the power off has not yet lead to dust on the sensor for me. So my real world experience suggests that the best thing to do is to turn the camera off.

Ya'll can do whatever you want. But I find it easy enough to turn the camera off.

Dust CAN be adhesive. Many different types of pollen can have a sticky coating on them, and living as I do in NYC I've found lots of "sticky" dirt blowing around. Say for instance a tiny bit of hair that's just been styled breaks off. It for sure would be "sticky". Dust from air condition filters can be sticky too. For this reason I use a foot pump and a narrow nozzle to "blow out" my cameras, the air stream is a lot more forceful than a rocket blower. It's also the reason I have pec pads and methanol.

It's so fast to turn the camera on and off that I'm not taking chances, I will turn it off before changing lenses. As a bonus on the K-7 when I turn it on it will clean the sensor if any dust got inside during the change. Possible risk of changing lenses while the camera is on is maybe damaging the internal focus motor if you press accidentally the shutter (could happen more easily with the external grip). Some people also reported possible SDM failures but it was not confirmed by Pentax officials.

Yeah, that is true. I've parked under a pollenating tree and seen it stick. Good point.

If Wheatfield doesn't have a problem with sensor dust, then maybe I've been wrong all this time. I imagine he changes lenses as much as anyone would.

But it is such an easy thing to do that I'll keep on turning the camera off.

I might just have really low standards too.
One thing to consider when reading my take on some of this stuff is that I live in a very dry climate, so while we do have dust issues, we don't have the humidity required to make dust stick to stuff.
I do take an admittedly very casual approach to a lot of this.